[NTG-context] Re: access image properties in Lua

[Alan Braslau via ntg-context <ntg-context@ntg.nl>]

On 13/07/23 13/07/23, 09:19, Hans Hagen wrote:
> On 7/11/2023 2:22 PM, Henning Hraban Ramm wrote:
>> What’s the current approved way to get image properties within a Lua 
>> function?
>>
>> very old:
>> local pic = figures.getinfo(figures.current().status.fullname)
>>
>> used to work in 2019:
>> local pic = img.scan{filename = figures.current().status.fullname}
>>
>> if I understand this right, "img" isn’t valid anymore:
>> """
>> token call, execute: grph-imagelib.lua:37: attempt to index a nil 
>> value (global 'img')
>> """
>>
>> I’d like to know the pixel size and if possible also the scaled target 
>> size of an image; either the "current" one or by name.
> \ctxlua{inspect(figures.getinfo("t:/sources/mill.png").used)}
> 
> \ctxlua{inspect(figures.getinfo("t:/sources/mill.png").status)}
> 
> etc .. no more faking the img lib
> 
> Hans

Hraban, Hans, and mailing list.

This is interesting. I would find it useful to be able to report these 
properties though a tracker - should be fairly easy if not already 
available.

One works with images having a certain resolution, whatever that may be. 
We also might have a target resolution, say 300 dpi or perhaps better 
for printing. As the images are typically resized when used, the 
resulting resolutions might be anything. Optimizing the resolutions of 
the source images can result in optimal PDF sizes, i.e. not too high nor 
too low resolution.

I can even imagine an automated workflow where high-resolution, say 2400 
dpi or even greater bitmap images, are supplied and the included bitmap 
could be "resampled" resulting in the inclusion of a targeted 
resolution. However, the reporting of the included, likely resized image 
resolutions then used to adjust or resample the source files externally 
and manually case-by-case would be sufficient.

Any suggestions on how to hook-in such reporting?

Bonus question: how also to handle the case of
\startMPcode
draw figure "MyFigure" xsized TextWidth ;
...
\stopMPcode

--
Alan
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